A computed tomography method and a corresponding computed tomography scanner for production of slice images with the aid of a plurality of X-ray beams at offset angles are generally known. In this context reference should be made in particular to the Laid-Open Specifications with the file references DE 103 54 900.5 (US 2005-0111623 A1) and DE 103 54 214 A1. The entire disclosure content of each of these laid open specifications are hereby incorporated herein by reference and are included in this description.
Both of the laid-open specifications mentioned above describe a method for reconstruction of tomographic slice images using detector data which is produced by at least two X-ray beams which are offset at an angle to one another and rotate with one another. In the first mentioned laid-open specification, complete 180° projection segments are produced from the detector data which is obtained by the two X-ray beams, can be associated with specific cycle phases of the scanned object, and can then be reconstructed to form slice image sequences. In the last-mentioned laid-open specification, it is proposed that image elements first of all be produced from small subsegments, which are combined with the correct timings to form segment image stacks, which are then added on a complementary angle-basis and in layers to form tomography slice images, which are produced from 180° segments overall.
Both methods have the common feature that, in total, data from a scanning interval of at least 180° overall is used to calculate the image from the detector data which is obtained by scanning with the aid of the at least two X-ray beams, with data from the detectors in each case being compiled with the correct angle and being used to achieve the optimum time resolution. In order to achieve the maximum time resolution, data which has been scanned over an angle of 90° is used from each X-ray beam, in the case of a computed tomography scanner with two X-ray beams offset through 90°.
By way of example, this type of scanning and the subsequent image production process make it possible to produce cardioimage sequences whose time resolution is sufficient to achieve diagnostically sufficiently relevant image statements, for example with respect to the coronaries, for a patient's heart which is beating at a normal speed. However, one problem which may occur in this case is that, in poor circumstances, the dose required to produce an effective image for diagnosis may not be sufficient for the best time resolution.